Wireless communication system, its base station and mobile station, communication synchronization management method and timer control program therefor

ABSTRACT

A mobile station which performs communication with a base station, the mobile station including: a timer timing a period to judge whether an uplink signal to the base station is synchronized, wherein the period is set by the base station for each of a plurality of mobile stations, wherein the timer restarts timing the period in response to receiving a timing adjustment value from the base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/525,722, filed Aug. 4, 2009, now published, which is a national stageof International Application No. PCT/JP2008/051685, filed Feb. 1, 2008,claiming priority based on Japanese patent application No. 2007-026203,filed on Feb. 5, 2007, the disclosure of which is incorporated herein inits entirety by reference thereto, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system whichmanages synchronization by use of a timer, and more particularly, to awireless communication system, its base station and mobile station, acommunication synchronization management method and a timer controlprogram therefore which enable the base station to adaptively control atransmit timing of an uplink signal from the mobile station.

BACKGROUND ART

In 3GPP Long Term Evolution (LTE), consideration is given to maintainingorthogonality between mobile stations (UE: user equipment) by allocatingan orthogonal radio resource to each mobile station (UE) whentransmitting and receiving data (a radio resource is an area uniquelydefined by time and frequency; radio resources are set by dividing timeand frequency into discrete areas for allocation to different mobilestations, so that one resource will not overlap between two mobilestations).

During transmission/reception of an uplink signal, in order to eliminateinterference between mobile stations (UE) within the cell of a basestation (Node B) so that the uplink signals can be demodulated correctlyby the base station (Node B), it is essential that the base station'sreceive timing of an uplink signals from each of a plurality of mobilestations (UE) fall within a guard interval called a “cyclic prefix(CP).” At the same time, regardless of whether synchronization in datatransmission/reception is actually being maintained, synchronization isassumed to be guaranteed if a receive timing falls within apredetermined timer period (i.e. during a timer is running). Based onthis assumption, a state in which a receive timing falls within thetimer period is judged to be a deemed in-sync state (i.e. a mobilestation is assumed to be uplink synchronized), and a state in which areceive timing does not fall within the timer period (i.e. a timerexpires) is judged to be a deemed out-of-sync state (i.e. a mobilestation is assumed to be NOT uplink synchronized).

A mobile station (UE) which has been determined to be in a deemedout-of-sync state sends a Non-sync RACH (Non-synchronized Random AccessChannel), in which a plurality of mobile stations (UE) compete for anduse common radio resources, before transmitting an uplink signal. Themobile station then receives from the base station a timing advance (TA)for adjusting its transmit timing. According to the TA, the mobilestation adjusts its transmit timing and finally synchronizes the uplinksignal (i.e. the uplink signal is received within a CP at the basestation).

Since each mobile station (UE) must secure synchronization while it istransmitting an uplink signal, a timing advance (TA) is notified fromthe base station to each mobile station, either at constant intervals ortriggered by the occurrence of a specific event (e.g., a rapid change inthe traveling speed of the mobile station). The reference time periodfrom when the timing advance (TA) is last updated until the mobilestation is judged to have returned to an out-of-sync state is eithernotified from the base station in the system information as the cellspecific value or is pre-defined as a fixed value. The reference time ismonitored at the base station and each of the mobile stations (UE)through use of a timer. Upon a timeout of the timer (i.e., when thereference time period described above expires), the mobile station (UE)is judged to have transited from a deemed in-sync state to a deemedout-of-sync state.

For the purpose of judging whether a mobile station (UE) is in a deemedin-sync state or a deemed out-of-sync state, the base station controlsas many timers as the number of mobile stations (UE) under itsmanagement. The mth timer held by the base station (where m is aninteger between 1 and M, and M is a natural number indicating the numberof mobile stations (UE) managed by the base station) corresponds to thetimer held by the mth mobile station (UE).

The plurality of timers controlled by the base station are set to thesame length of time, so are the timers held by the plurality of mobilestations. The base station timers and the mobile station timers are setto a timer length such that synchronization can be guaranteed by themobile station (UE) that is traveling at the highest speed (e.g., 350km/h) of all the mobile stations (UE) supported by the base station. Thetimer length is therefore shorter than the minimum length of time overwhich this mobile station (UE) will become out-of-sync. A determinationbetween a deemed in-sync state and a deemed out-of-sync state is madesolely relying on the state of the timer, regardless of the actualtraveling speed of the mobile station (UE). Non-patent Literature 1discloses an example of a process for adjusting a transmit timing duringtransfer of an uplink signal in the 3GPP Long Term Evolution (LTE)described above.

When data is generated for transmission to the base station, a mobilestation (UE) in a deemed in-sync state first transmits a SchedulingRequest (SR) to the base station to request a radio resource over whichto transmit the data, using a radio resource specific to the mobilestation (UE). One method that can be used to assign a radio resourcespecific to a mobile station (UE) is to periodically assign a radioresource over which to transmit an SR to each of the mobile stations(UE) that are in a deemed in-sync state. On the other hand, when amobile station (UE) in a deemed out-of-sync state transmits an SR, itfirst transmits a Non-sync RACH and receives a timing advance (TA) forcontrolling the transmit timing and, at the same time, assigns a radioresource specific to the mobile station (UE) over which to transmit theSR.

It is clear from the foregoing that a mobile station (UE) in a deemedout-of-sync state suffers a longer latency (or a delay due to waitingtime) before it can initiate data transmission than a mobile station ina deemed in-sync state. This is because the former mobile stationadditionally requires a step of transmitting a Non-sync RACH beforebeing able to perform a step of transmitting an SR. In addition, sinceorthogonality between mobile stations (UE) is not guaranteed for aNon-sync RACH, a collision may occur between mobile stations (UE). If acollision occurs, the transmitted Non-sync RACH may not be detected bythe base station, in which case the mobile station (UE) must retransmita Non-sync RACH. This further increases the latency.

-   Non-patent Literature 1 3GPP RAN WG2 Contribution [R2-063401.doc NTT    DoCoMo]    http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_(—)56/Documents/-   Non-patent Literature 2 3GPP RAN WG1 Contribution [R1-063377.doc    Nokia]    http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_(—)47/Docs/-   Non-patent Literature 3 3GPP RAN WG1 Contribution [R1-063405.doc    Siemens]    http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1_(—)47/Docs/

In the related art described above, the timer length is set based on thetime in which synchronization is guaranteed by a rapidly traveling (forexample, at a speed of 350 km/h) mobile station (UE). This leads to aproblem in which a mobile station (UE) that is standing still ortraveling at a low speed may be judged to be in a deemed out-of-syncstate upon a timeout of the timer, even though the actual uplinksynchronization is being maintained.

Furthermore, if another data occurs at the mobile station (UE) and anuplink signal must be transmitted during a period in which the timer hastimed out but synchronization is actually being maintained, the latencybefore the data can be transmitted becomes even longer.

This is because a static or slow-moving mobile station (UE) is judged tobe out-of-sync based on the timer, even though it is actually in syncand can transmit a Scheduling Request (SR) using a radio resourcespecifically assigned to it. In such situation, the mobile station needsfirst to transmit a Non-sync RACH to receive a timing advance (TA) fromthe base station (Node B), so that it can be assigned a radio resourceover which to transmit the SR according to the timing advance (TA).

OBJECTS OF INVENTION

An object of the present invention is to provide a wirelesscommunication system, its base station and mobile station, acommunication synchronization management method and a timer controlprogram therefor which can control the timer length used for judgingwhether a mobile station is in a deemed in-sync state or in a deemedout-of-sync state adaptively for each a mobile station, therebyminimizing possibilities for an actually in-sync mobile station to bejudged to be in a deemed out-of-sync state.

Another object of the present invention is to provide a wirelesscommunication system, its base station and mobile station, acommunication synchronization management method and a timer controlprogram therefor which can reduce a latency in transmission of an uplinksignal during a period in which a mobile station in a deemed out-of-syncstate is actually in sync.

SUMMARY

According to a first exemplary aspect of the invention, a base stationof a wireless communication system which performs wireless communicationbetween a mobile station and a base station, comprises

a timer unit which sets a period, during which synchronization of areceive timing at the base station for an uplink signal from the mobilestation is guaranteed, and, according to the occurrence ornon-occurrence of a timeout of the period, judges whether the mobilestation is in a deemed in-sync state, in which uplink synchronization isguaranteed, or in a deemed out-of-sync state, in which uplinksynchronization is not guaranteed, and

a timer control unit which is made capable of determining the period ofthe timer unit for each mobile station according to the state of themobile station and updating the timer unit.

According to a second exemplary aspect of the invention, a mobilestation of a wireless communication system which performs wirelesscommunication between a mobile station and a base station, comprises

a timer unit which sets a period, during which synchronization of areceive timing at the base station for an uplink signal from the mobilestation is guaranteed, and, according to the occurrence ornon-occurrence of a timeout of the period, judges whether the mobilestation is in a deemed in-sync state, in which uplink synchronization isguaranteed, or in a deemed out-of-sync state, in which uplinksynchronization is not guaranteed, and

a timer control unit which is made capable of determining the timerlength according to the state of the mobile station and updating thetimer unit.

According to a third exemplary aspect of the invention, a wirelesscommunication system which performs wireless communication between amobile station and a base station, comprises

the base station and the mobile station

comprising a timer unit which sets a period, during whichsynchronization of receive timings at the base station for uplinksignals from the mobile station is guaranteed and, according to theoccurrence or non-occurrence of a timeout of the period, judges whetherthe mobile station is in a deemed in-sync state, in which uplinksynchronization is guaranteed, or in a deemed out-of-sync state, inwhich uplink synchronization is not guaranteed, and

at least either of the base station and the mobile station

comprising a timer control unit which is made capable of determining thetimer length of at least either of the base station and the mobilestation adaptively for each mobile station according to the state of themobile station and updating the timer unit.

According to a fourth exemplary aspect of the invention, a communicationsynchronization management method in wireless communication system toperform wireless communication between a mobile station and a basestation, comprises

at the base station and the mobile station

having a timer step of setting a period, during which synchronization ofa receive timing at the base station for an uplink signal from themobile station is guaranteed, and, according to the occurrence ornon-occurrence of a timeout of the period, judging by a timer whetherthe mobile station is in a deemed in-sync state, in which uplinksynchronization is guaranteed, or in a deemed out-of-sync state, inwhich uplink synchronization is not guaranteed, and

at least one of the base station and the mobile station

determining the period used in the timer step at least either of thebase station and the mobile station adaptively for each mobile stationaccording to the state of the mobile station and updating the timer.

According to a fifth exemplary aspect of the invention, a timer controlprogram which is realized by a computer of a wireless communicationsystem which performs wireless communication between a mobile stationand a base station for operating on the base station,

causing the computer to execute

a function to set a period, during which synchronization of a receivetiming at the base station for an uplink signal from the mobile stationis guaranteed, and, according to the occurrence or non-occurrence of atimeout of the period, judge by a timer whether the mobile station is ina deemed in-sync state, in which uplink synchronization is guaranteed,or in a deemed out-of-sync state, in which uplink synchronization is notguaranteed, and

a timer control function which is made capable of determining the timerlength for each mobile station according to the state of the mobilestation and updating the timer.

According to a sixth exemplary aspect of the invention, a timer controlprogram which is realized by a computer of a wireless communicationsystem which performs wireless communication between a mobile stationand a base station for operating on the mobile station,

causing the computer to execute

a function to set a period, during which synchronization of a receivetiming at the base station for an uplink signal from the mobile stationis guaranteed, and, according to the occurrence or non-occurrence of atimeout of the period, judge by a timer whether the mobile station is ina deemed in-sync state, in which uplink synchronization is guaranteed,or in a deemed out-of-sync state, in which uplink synchronization is notguaranteed, and

a timer control function which is made capable of determining the timerlength according to the state of the mobile station and updating thetimer.

Effect of the present invention is that the probability can be reducedthat a latency before data transmission increases when a mobile stationthat is actually in sync is judged to be out of sync based on a timeoutof the timer used for judging whether a mobile station is in a deemedin-sync state or in a deemed out-of-sync state. This is because thepresent invention can control the timer length of each mobile stationadaptively to the traveling speed of the mobile station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for explaining a first exemplary embodiment ofthe present invention;

FIG. 2 is a block diagram for explaining the synchronization timeraccording to the first exemplary embodiment of the present invention;

FIG. 3 is a block diagram for explaining the timer adaptive control partaccording to the first exemplary embodiment of the present invention;

FIG. 4 is a block diagram for explaining the method to estimate thetraveling speed of a mobile station;

FIG. 5 is a block diagram for explaining correlations between timingadvance values for receive timing and transmit timing;

FIG. 6 is a diagram for explaining the table which defines correlationsbetween traveling speed and timer length, based on which a timer lengthis determined, according to the first exemplary embodiment of thepresent invention;

FIG. 7 is a diagram for explaining the method to determine a timerlength according to the first exemplary embodiment of the presentinvention;

FIG. 8 is a diagram for explaining the method to determine a timerlength according to the first exemplary embodiment of the presentinvention;

FIG. 9 is a diagram for explaining the procedure to determine a timerlength according to the first exemplary embodiment of the presentinvention;

FIG. 10 is a block diagram for explaining the timer adaptive controlpart according to the first exemplary embodiment of the presentinvention;

FIG. 11 is a diagram for explaining the table which defines correlationsbetween timing advance and timer length, based on which a timer lengthis determined, according to the first exemplary embodiment of thepresent invention;

FIG. 12 is a diagram for explaining the method to determine a timerlength according to the first exemplary embodiment of the presentinvention;

FIG. 13 is a diagram for explaining the method to determine a timerlength according to the first exemplary embodiment of the presentinvention;

FIG. 14 is a block diagram for explaining the timer adaptive controlpart according to the first exemplary embodiment of the presentinvention;

FIG. 15 is a flow chart showing the operation of the base stationaccording to the first exemplary embodiment of the present invention;

FIG. 16 is a flow chart showing the operation of the base stationaccording to the first exemplary embodiment of the present invention;

FIG. 17 is a flow chart showing the operation of the base stationaccording to the first exemplary embodiment of the present invention;

FIG. 18 is a block diagram showing a hardware structure of the mobilestation and the base station according to the first exemplary embodimentof the present invention;

FIG. 19 is a block diagram for explaining a second exemplary embodimentof the present invention;

FIG. 20 is a block diagram for explaining the timer adaptive controlpart according to the second exemplary embodiment of the presentinvention;

FIG. 21 is a block diagram for explaining the timer adaptive controlpart according to the second exemplary embodiment of the presentinvention;

FIG. 22 is a block diagram for explaining the timer adaptive controlpart according to the second exemplary embodiment of the presentinvention;

FIG. 23 is a diagram for explaining the procedure to determine a timerlength according to the second exemplary embodiment of the presentinvention;

FIG. 24 is a block diagram for explaining a third exemplary embodimentof the present invention;

FIG. 25 is a block diagram for explaining the timer adaptive controlpart according to the third exemplary embodiment of the presentinvention;

FIG. 26 is a diagram for explaining the procedure to determine a timerlength according to the third exemplary embodiment of the presentinvention;

FIG. 27 is a block diagram for explaining a fourth exemplary embodimentof the present invention;

FIG. 28 is a block diagram for explaining the timer adaptive controlpart according to the fourth exemplary embodiment of the presentinvention;

FIG. 29 is a diagram for explaining the procedure to determine a timerlength according to the fourth exemplary embodiment of the presentinvention;

FIG. 30 is a block diagram showing the system structure of a wirelesscommunication system according to a fifth exemplary embodiment of thepresent invention;

FIG. 31 is a block diagram showing the system structure of a wirelesscommunication system according to a sixth exemplary embodiment of thepresent invention;

FIG. 32 is a block diagram showing the system structure of a wirelesscommunication system according to a seventh exemplary embodiment of thepresent invention;

FIG. 33 is a diagram illustrating a schematic concept of a wirelesscommunication system according to an eighth exemplary embodiment of thepresent invention;

FIG. 34 is a diagram illustrating a schematic concept of a wirelesscommunication system according to a ninth exemplary embodiment of thepresent invention; and

FIG. 35 is a diagram illustrating a schematic concept of a wirelesscommunication system according to a tenth exemplary embodiment of thepresent invention.

EXEMPLARY EMBODIMENT

The present invention will now be described in detail with reference tothe drawings.

First, in exemplary embodiments of the present invention, an initialvalue T_(TM0) for the timer, which is used for judging whether a mobilestation is in a deemed in-sync state or in a deemed out-of-sync state,is set during a period in which synchronization of a rapidly movingstation can be guaranteed. This can be done by using a method similar tocommonly used methods. In 3GPP LTE, a traveling speed of 350 [km/h] isassumed as a reference speed for setting a timer length.

In Non-patent Literature 2, the tolerance for deviations in transmittiming required for an uplink signal to be detected correctly isestimated to be approximately 1 [usec]. In Non-patent Literature 3, theworst case for synchronization loss is assumed to be whensynchronization is lost as a result of a deviation of 1 [usec] intransmit timing.

Using these values as reference, each exemplary embodiment uses approx.1.5 [sec] as the initial value T_(TM0) for the timer. This is the lengthof time which causes transmit timing to deviate by 1 [usec] at atraveling speed of 350 [km/h]. The timer length set on the mth firsttimer (first timer #m) held by the base station (Node B) and the timerlength set on the second timer held by the mth mobile station (UE #m)are the same, where m is an integer between 1 and M, and M is a naturalnumber representing the number of mobile stations under management ofthe mobile station. A random access signal transmitted by a mobilestation in an out-of-sync state consists of a sequence randomly selectedfrom a predetermined number of sequences (for example, the Zadoff-Chusequence).

“Synchronization” as used herein refers to a state in which a transmittiming is controlled by the base station so that a receive timing atwhich an uplink signal is transmitted from the mobile station to thebase station falls within the required accuracy. The receive timingvaries depending on such factors as the distance between the mobilestation and the base station, i.e., the position of the mobile station.Therefore, a higher traveling speed of the mobile station results in agreater variation in the receive timing and consequently in a shorterlength of time during which “synchronization” is maintained.

A distinction between a “deemed in-sync state” and a “deemed out-of-syncstate” is judged based on whether the timer is running or expired. A“deemed in-sync state” is a state in which the timer is running and,based on this fact, it is judged that uplink synchronization between themobile station and the base station can be guaranteed. A “deemedout-of-state” is a state in which the timer has expired and, based onthis fact, it is judged that uplink synchronization between the mobilestation and the base station cannot be guaranteed. This means that, evenwhen a mobile station is judged to be in a “deemed out-of-sync state,”it may actually be in sync. To the contrary, even when a mobile stationis judged to be in a “deemed in-sync state,” it may actually be out ofsync.

Although the exemplary embodiments below are described with respect to3GPP LTE as an example, the target of the present invention is notlimited to LTE but can be wireless LAN, WiMAX or other similartechnology. The present invention can be applied to any system whichrequires TDM-based synchronous connection and on which a deviationbetween transmit and receive timings can occur.

First Exemplary Embodiment

FIG. 1 is a block diagram showing the system structure of a wirelesscommunication system according to the first exemplary embodiment of thepresent invention. In this exemplary embodiment, the calculation of anindicator value for determining a timer length, as well as thedetermination of the length of the first timer held by the base stationand the second timer held by the mobile station (UE), are performed bythe base station.

With reference to FIG. 1, the mobile station (UE) 101 comprises adetermination part 103, a basic signal generation part 104, an uplinksignal generation part 105, a transmit information input part 106, asignal transmission part 107, a second timer 108 and a downlink signaldemodulation part 109.

At the mobile station (UE #m) 101, the downlink signal demodulation part109 receives from the base station (Node B) 102 a downlink receivesignal S_(DLTX) which contains a timing advance (TA) for a uplinktransmit timing, and outputs the reproduced timing advance (TA) S_(RTA),which corresponds to the received timing advance (TA) at the mobilestation; timer control information S_(TCI), which notifies a reset ofthe second timer when a timing advance (TA) is notified from the basestation (Node B); and reproduced timer update information S_(RTUI),which corresponds to the timer update information indicating a new timerlength in case the second timer is updated.

The second timer 108 operates according to the timer control informationS_(TCI) and the reproduced timer update information S_(RTUI). When thereproduced timer update information S_(RTUI) is inputted, the secondtimer 108 updates the length of the second timer, and outputs as stateinformation S_(SI) the information as to whether the mobile station (UE)#m is in a deemed in-sync state or in a deemed out-of-sync state. Thesecond timer 108 may perform the process to output state informationS_(SI) in such a manner that, for example, it outputs state informationS_(SI) only when the mobile station is in a deemed out-of-sync state anddoes not output state information S_(SI) when the mobile station is in adeemed in-sync state.

When transmit information S_(INFO) to be transmitted to the base station(Node B) 102 is inputted, the determination part 103 switches connectionaccording to the state information S_(SI). More specifically, itswitches connection to the uplink signal generation part 105 if theinformation indicates a deemed in-sync state or to the basic signalgeneration part 104 if the information indicates a deemed out-of-syncstate.

The basic signal generation part 104 has a function to generate andoutput a basic signal for use in communication with the base station(Node B) 102. In the example used in this and the other exemplaryembodiments described below, a random access signal S_(RS) is generatedand outputted in order to receive a timing advance (TA) from the basestation (Node B) for synchronizing an uplink signal.

The uplink signal generation part 105 adjusts the transmit timingaccording to the reproduced timing advance (TA) S_(RTA), and generatesand outputs an uplink signal S_(US) that contains the transmitinformation S_(INFO).

As an uplink transmit signal S_(ULTX), the signal transmission part 107transmits the uplink signal S_(US) if the mobile station is in a deemedin-sync state or the random access signal S_(RS) if the mobile stationis in a deemed out-of-sync state.

Referring to FIG. 1, the base station (Node B) 102 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 112, a timing calculation part 113, a timeradaptive control part 114, a synchronization timer 115, where asynchronization timer may be called as Time Alignment Timer instead, anda downlink transmission part 116.

At the base station (Node B) 102, the determination part 110 switchesconnection according to the state information S_(SI) which indicates thestate of the mobile station (UE) #m. More specifically, it switchesconnection to the uplink signal demodulation part 112 if the informationindicates a deemed in-sync state or to the basic signal demodulationpart 111 if the information indicates a deemed out-of-sync state.

The basic signal demodulation part 111 receives an input of an uplinkreceived signal S_(ULTX), which corresponds to a basic signal, and has afunction to demodulate and output the inputted uplink received signalS_(ULTX). In the example used in this and the other exemplaryembodiments described below, the basic signal demodulation part 111receives as input an uplink received signal S_(ULTX) which correspondsto a random access signal S_(RS), and outputs as random access detectioninformation S_(RDI) the information which indicates a sequence exceedingthe pre-defined detection threshold.

The uplink signal demodulation part 112 demodulates an uplink receivedsignal S_(ULTX), which corresponds to an uplink signal S_(US), andoutputs reproduced transmit information S_(RINFO), which corresponds totransmit information S_(INFO).

The timing calculation part 113 has a TA calculation part 1131 and a TAstorage part 1132. The timing calculation part 113 uses the TAcalculation part 1131 to detect the receive timing (i.e., a deviation inthe receive timing) for an uplink received signal S_(ULTX), andcalculates a timing advance (TA) S_(TA) to notify to the mobile station(UE) #m based on the detected receive timing. It then stores theresultant TA in the TA storage part 1132 and outputs this TA S_(TA).

The timer adaptive control part 114, using as input both or either of anuplink received signal S_(ULTX) and/or a timing advance (TA) S_(TA),determines the length of the first timer #m and the second timer of themobile station (UE) #m. It then outputs the resultant timer length astimer update information S_(TUI), as well as the information whichnotifies a reset of the first timer #m by sending a timing advance (TA)to the mobile station (UE) #m as timer control information S_(TCI).

The synchronization timer 115, which has M first timers, operatesaccording to the timer update information S_(TUI) and the timer controlinformation S_(TCI), and outputs as state information S_(SI) theinformation as to whether the mobile station (UE) #m is in a deemedin-sync state or in a deemed out-of-sync state.

The downlink transmission part 116, according to the state informationS_(SI), generates and transmits a downlink transmit signal S_(DLTX). Thedownlink transmit signal S_(DLTX) contains a timing advance (TA) S_(TA)and timer update information S_(TUI) in the case of a deemed in-syncstate or contains a timing advance (TA) S_(TA), a timer updateinformation S_(TUI) and random access detection information S_(RDI) inthe case of a deemed out-of-sync state.

The synchronization timer consists of M first timers 117, as shown inFIG. 2. The first timer #m corresponds to the second timer of the mobilestation (UE) #m.

When determining the length of the first timer #m and the second timerof the mobile station (UE) #m, the timer adaptive control part 114 usesas an indicator both or either of a traveling speed S_(VI), which is theresult obtained by estimating the traveling speed of the mobile station(UE) #m, and/or transmit timing variation information S_(TADI), which isthe result obtained by calculating a time variation for the timingadvance (TA).

FIGS. 3, 10 and 14 show the structure of the timer adaptive control partwhen using as an indicator a traveling speed; a time variation in timingadvance (TA); or a traveling speed and a time variation in a timingadvance (TA), respectively.

The timer adaptive control part 114 of FIG. 3 comprises a speedestimation part 118, which estimates the traveling speed S_(VI) of themobile station (UE) #m by using as input an uplink received signalS_(ULTX), and a timer determination part 121, which determines by usingthe traveling speed S_(VI) as input the length of the first timer #m andthe length of the second timer of the mobile station (UE) #m.

One estimation method for a traveling speed that can be used here is toestimate it from a Doppler frequency F_(d) [Hz] (where F_(d) is a realnumber equal to or greater than 0).

A Doppler frequency F_(d) can be estimated by using the phase rotatingamount θ [rad] (where θ is a real number equal to or greater than 0) ofa known pilot symbol. For example, as shown in FIG. 4, when it isassumed that P₁ and P₂ are received signal vectors corresponding to thefirst and second pilot symbols, respectively, and that T_(P) is atime-domain interval between P₁ and P₂, a phase rotating amount θ can beobtained from a relational expression: θ={cos⁻¹(P₁·P₂)}/T_(P) (where ·is an inner product). Using the value of θ thus obtained, a Dopplerfrequency F_(d) can be obtained from a relational expression:F_(d)=θ/{2πT_(P)}. Furthermore, using the Doppler frequency F_(d) thusobtained, a traveling speed v can be calculated from a relationalexpression: v=F_(d)λ=F_(d)(c/f), where λ is a wavelength [m], c is thelight speed 3×10⁸ [m/s] and f is a carrier frequency [Hz].

FIG. 5 shows an example correlation between a receive timing detected bythe base station (Node B) and a timing advance (TA) for a transmittiming to be notified to the mobile station (UE).

In FIG. 5, a cyclic prefix (CP) is added to the head of an uplink signal(1 frame). The ideal receive timing is such that the head of the CPcomes at the head of each time slot. A deviation x [us] of the receivetiming actually detected from the ideal receive timing occurs due tosuch factors as the movement of the mobile station (UE) and deviation ina transmit timing.

The amount of deviation in a transmit timing may be notified to themobile station (UE) using either of the following two methods: onemethod is to notify the absolute value of x [us] as a timing advance(TA); and another is to notify a value obtained by time-dividing x [us]as a timing advance (TA). In the method to notify a time division value,it is notified that one transmission of timing advance (TA) will beadvanced or delayed by y [us] units of a pre-defined constant step.Thus, in the case of the method to notify a time division value, atransmit timing may be transmitted using 1 bit to notify, for example,that the fixed value will be advanced by y [us] if the transmitted valueis 0 or the fixed value will be delayed by y [us] if the transmittedvalue is 1. In this case, if the actually calculated amount of deviationin a transmit timing is +4×y [us], a value of 0 is transmitted fourtimes so that the transmit timing will be advanced by 4×y [us] in total.

There is another method that combines these two methods. A possiblecombination is to use the method to notify an absolute value whensetting an initial value for a transmit timing and the method to notifya time-division value when updating the transmit timing.

FIGS. 6 to 8 are diagrams for explaining the method to determine andupdate the length of the first and second timers according to the firstexemplary embodiment.

The timer adaptive control part 114 is assumed to comprise a speedestimation part 118 and a timer determination part 121 (FIG. 3). Thetimer determination part 121 determines the length of the first andsecond timers, based on the traveling speed S_(VI) and the table whichpre-defines correlations between traveling speed and timer length. Thisexemplary embodiment uses the table shown in FIG. 6 which definescorrelations between traveling speed and timer length.

Each of the timer lengths in the table of FIG. 6 has been calculatedusing the expression (1) below, and indicates the time [sec] ofdeviation caused at each traveling speed in the same transmit timingvalue as the transmit timing value assumed to deviate by 1.5 [sec] at atraveling speed of 350 [km/h], which is the reference speed used whensetting the initial value.

$\begin{matrix}\left( {{EXPRESSION}\mspace{14mu} 1} \right) & \; \\{{D_{TA}\left\lbrack {u\mspace{11mu}\sec} \right\rbrack} = {{v\left\lbrack {{km}\text{/}h} \right\rbrack} \times \frac{1}{3600} \times {t\left\lbrack \sec \right\rbrack} \times {6.7\left\lbrack {u\mspace{11mu}\sec\text{/}{km}} \right\rbrack}}} & (1)\end{matrix}$

where D_(TA) [usec] is the value of deviation in transmit timing; v[km/h] is the traveling speed of the mobile station (UE); t [sec] is thetime which causes a deviation of D_(TA); and 6.7 [usec/km] is a RoundTrip Delay (RTD), which is a propagation delay caused between the basestation (Node B) and the mobile station (UE).

The expression (1) is used to create a table as shown in FIG. 6. Thetable is created by first determining the increments of the thresholdfor traveling speed v and the acceptable amount of transmit timingdeviation D_(TA), and then substituting the resultant values tocalculate t in the expression (1). The value of t thus obtained is usedas a timer length.

In this exemplary embodiment, the speed estimation part 118 of the basestation (Node B) estimates the traveling speeds of the two mobilestations (UE #1, UE #2) at regular time intervals as shown in FIG. 7.The timer determination part 121 determines the length of the first andsecond timers at each of the times (t₀, t₁, t₂, t₃). Based on theresults, the first and second timers are controlled adaptively. It isassumed here that the initial value T_(TM0) for all the pairs of thefirst and second timers is 1.5 [sec], which is the length of timedetermined to deal with a traveling speed of 350 [km/h].

In FIG. 7, the mobile station (UE) #1 will first be considered. Thetraveling speed at t₀ is 40 [km/h]. This is much lower than thetraveling speed 350 [km/h] targeted by the initial value for all thefirst and second timer pairs, implying that synchronization willcontinue for a longer period. In this case, the length of the firsttimer #1 and the second timer of the mobile station (UE) #1 can be madelonger.

Referring to the table of FIG. 6, the traveling speed of 40 [km/h] isbetween 30 [km/h] to 120 [km/h], so the length of the first timer #1 andthe second timer of the mobile station (UE) #1 is determined to be 4.5[sec].

The base station (Node B) notifies to the mobile station (UE) #1 thetimer update information indicating that the timing advance (TA) and thelength of the second timer will be updated to 4.5 [sec]. Immediatelyafter issuing this notification, it updates the length of the firsttimer #1 to 4.5 [sec] and causes the first timer #1 to start operatingagain.

The mobile station (UE) #1 demodulates the downlink signal to reproducethe timing advance (TA) and the timer update information, updates thelength of the second timer to 2.9 [sec] and causes the second timer tostart operating again.

Similarly, the lengths of the first timer #1 and the second timer of themobile station (UE) #1 at t=t₁, t₂, t₃ are determined to be 17.9 [sec],4.5 [sec] and 1.5 [sec], respectively. Every time the timer length isupdated, the base station (Node B) notifies to the mobile station (UE)#1 the new length of the second timer thus determined.

Next, the mobile station (UE) #2 will be considered. Its initial valueis the same as the mobile station (UE) #1, i.e., 1.5 [sec]. Thetraveling speed at t₀ is 4 [km/h]. This speed is even lower than themobile station (UE) #1. The timer length can be made longer becausesynchronization will continue for a longer period than the mobilestation (UE) #1.

Referring to the table of FIG. 6, the traveling speed of 4 [km/h] isbetween 0 [km/h] to 5 [km/h], so the length of the first timer #2 andthe second timer of the mobile station (UE) #2 is determined to be 107.5[sec].

The base station (Node B) notifies to the mobile station (UE) #2 thetimer update information indicating that the timing advance (TA) and thelength of the second timer will be updated to 107.5 [sec]. Immediatelyafter issuing this notification, it updates the length of the firsttimer #2 to 107.5 [sec] and causes the first timer #1 to start operatingagain.

The mobile station (UE) #2 demodulates the downlink signal to reproducethe timing advance (TA) and the timer update information, updates thelength of the second timer to 107.5 [sec] and causes the second timer tostart operating again.

Similarly, estimation of the traveling speeds at t=t₁, t₂, t₃ results in3 [km/h], 2 [km/h] and 2 [km/h], which are almost the same as the resultfor t₀. Therefore, the timer setting over the observation period of FIG.7 is determined to remain the same at 107.5 [sec] without the need ofany update. The base station (Node B) and the mobile station (UE) #2respectively repeat the process of resetting the length of the firsttimer #2 or the second timer and causing the respective timers to startoperating again, every time the timing advance (TA) is calculated ornotified.

FIG. 8 shows the results of determining the timer length as describedabove.

FIG. 9 is a diagram showing the part of the process performed by thebase station (Node B) and the mobile station (UE) #m according to thisexemplary embodiment which relates to the determination of the length ofthe first timer #m and the second timer of the mobile station (UE) #m.

After receiving an uplink signal 1 from the mobile station (UE) #m, thebase station (Node B) calculates a timing advance (TA), estimates thetraveling speed and determines the length of the first timer #m and thesecond timer of the mobile station (UE) #m. The base station (Node B)then notifies to the mobile station (UE) #m the timing advance (TA) andthe updated length of the second timer via a downlink signal 1.Immediately after transmitting the downlink signal 1 to the mobilestation (UE) #m, the base station (Node B) resets the first timer #m andcauses the first timer #m to start operating again.

The mobile station (UE) #m demodulates the downlink signal 1 toreproduce the timing advance (TA) and the updated second timer length.After updating the second timer to the reproduced timer length, themobile station (UE) #m resets the second timer and causes the secondtimer to start operating again. The mobile station (UE) #m then adjuststhe transmit timing according to the reproduced timing advance (TA) andtransmits an uplink signal 2.

A possible signal that can be used by the speed estimation part of thebase station (Node B) for estimation of a traveling speed is a knownsignal (Reference Signal: RS) for demodulating the data from the mobilestation (UE) transmitted via the Uplink Shared Channel (UL-SCH) and theuplink signal including the control information, or an RS for CQImeasurement which is transmitted to allow the base station (Node B) tomeasure the quality of an uplink line (Channel Quality Indicator: CQI)transmitted via a UL-SCH. Also, a possible signal for notifying a timerupdate is a signal for controlling Layer 1/Layer 2 (L1/L2 controlsignaling) transmitted via a Downlink Shared Channel (DL-SCH), or asignal for data transmission (Physical Downlink Shared Channel: PDSCH)transmitted via a DL-SCH.

The timer adaptive control part 114 of FIG. 10 comprises a variationcalculation part 119, which calculates and outputs the time variationS_(TADI) in the timing advance (TA) by using a timing advance (TA)S_(TA) as input, and a timer determination part 122, which determines byusing the time variation S_(TADI) in the timing advance (TA) as inputthe length of the first timer #m and the length of the second timer ofthe mobile station (UE) #m.

In the method according to the present invention which uses a timevariation in a timing advance (TA) as an indicator for determining atimer length, if an absolute value of the amount of deviation in atransmit timing is notified as a timing advance (TA), the amount ofvariation in a timing advance (TA) over an observation period isdirectly used as the time variation in the timing advance (TA). On theother hand, if a time-divided value of the amount of deviation in atransmit timing is notified as a timing advance (TA), the time-dividedvalues of the timing advance (TA) are summed up to reproduce the actualamount of deviation in the transmit timing, and the amount of variationof the reproduced transmit timing over an observation period is used asa time variation in the timing advance (TA).

The timer determination part 122 determines the length of the first andsecond timers, based on the time variation in the timing advance (TA)and the table which pre-defines correlations between time variation intiming advance (TA) and timer length. In the description of thisexemplary embodiment, the method to notify the amount of deviation in atiming advance (TA) as an absolute value will be considered.

Each of the timer lengths in the table of FIG. 11 has been calculatedusing the expressions (2) to (4) below, based on different correlationsbetween an amount of deviation in transmit timing during an observationinterval and a traveling speed at which such amount of deviation isexpected to occur.

$\begin{matrix}\left( {{EXPRESSION}\mspace{14mu} 2} \right) & \; \\{{D_{TA}\left\lbrack {u\mspace{11mu}\sec} \right\rbrack} = {{v\left\lbrack {{km}\text{/}h} \right\rbrack} \times \frac{1}{3600} \times {t\left\lbrack \sec \right\rbrack} \times {6.7\left\lbrack {u\mspace{11mu}\sec\text{/}{km}} \right\rbrack}}} & (2) \\\left( {{EXPRESSION}\mspace{14mu} 3} \right) & \; \\{{v\left\lbrack {{km}\text{/}h} \right\rbrack} = {\frac{1}{6.7\left\lbrack {u\mspace{11mu}\sec\text{/}{km}} \right\rbrack} \times \frac{3600}{\Delta\;{t\left\lbrack \sec \right\rbrack}} \times \Delta\;{d\left\lbrack {u\mspace{11mu}\sec} \right\rbrack}}} & (3) \\\left( {{EXPRESSION}\mspace{14mu} 4} \right) & \; \\{{D_{TA}\left\lbrack {u\mspace{11mu}\sec} \right\rbrack} = {{t\left\lbrack \sec \right\rbrack} \times \frac{\Delta\;{d\left\lbrack {u\mspace{11mu}\sec} \right\rbrack}}{\Delta\;{t\left\lbrack \sec \right\rbrack}}}} & (4)\end{matrix}$

where, in the expression (2), D_(TA) [usec] is the value of deviation inthe transmit timing; v [km/h] is the traveling speed of the mobilestation (UE); t [sec] is the time which causes a deviation of D_(TA);and 6.7 [usec/km] is a Round Trip Delay (RTD), which is a propagationdelay caused between the base station (Node B) and the mobile station(UE). In the expression (3), Δ d [usec] is the amount of deviation inthe transmit timing caused over a period of Δt [sec].

Suppose that the variation calculation part of the base station (Node B)calculates a time variation in a timing advance (TA) at regular timeintervals, i.e., per 10 [sec], for a mobile station (UE) #1 and that theresults are as shown in FIG. 12. At each of the times (t₀, t₁, t₂, t₃),the timer determination part determines the length of the first andsecond timers and controls the first and second timers adaptively. It isassumed here that the initial value T_(TM0) for the first and secondtimers is 1.5 [sec], which is the length of time determined to deal witha traveling speed of 350 [km/h].

The time variation in the timing advance (TA) at t₀ calculated by thevariation calculation part of the base station (Node B) is 2.18 [usec/10sec]. Referring to the table of FIG. 11, the variation is between 0.56[usec/10 sec] to 2.23 [usec/10 sec], so the timer length can be madelonger than the initial value 1.5 [sec]. Based on the table, the lengthof the first and second timer #1 is determined to be 4.5 [sec].

The base station (Node B) notifies to the mobile station (UE) #1 thetimer update information indicating that the timing advance (TA) and thelength of the second timer will be updated to 4.5 [sec]. Immediatelyafter issuing this notification, it updates the length of the firsttimer #1 to 4.5 [sec] and causes the first timer #1 to start operatingagain.

The mobile station (UE) #1 demodulates the downlink signal to reproducethe timing advance (TA) and the timer update information, updates thelength of the second timer to 2.9 [sec] and causes the second timer tostart operating again.

Similarly, at t=t₁, t₂, t₃, the results obtained by the base station(Node B) from the calculation of the time variation in the timingadvance (TA) are 1.45 [usec/10 sec], 1.92 [usec/10 sec] and 3.28[usec/10 sec]. Referring to the table of FIG. 11, it can be determinedthat the lengths of the first and second timers are 4.5 [sec], 4.5 [sec]and 1.5 [sec], respectively.

FIG. 13 shows the results of determining the timer length as describedabove.

The timer adaptive control part 114 of FIG. 14 comprises a speedestimation part 118, which estimates the traveling speed S_(VI) of themobile station (UE) #m by using as input an uplink received signalS_(ULTX); a variation calculation part 119, which calculates and outputsthe time variation S_(TADI) in the timing advance (TA) by using as inputa timing advance (TA) S_(TA); and a timer determination part 120, whichdetermines the length of the first timer #m and the length of the secondtimer of the mobile station (UE) #m by using as input the travelingspeed S_(VI) and the time variation S_(TADI) in the timing advance (TA).The timer adaptive control part 114 determines the length of the firsttimer #m and the second timer of the mobile station (UE) #m, using themethod explained with reference to FIGS. 3 and 10. In the case whereboth the traveling speed S_(VI) and the time variation S_(TADI) in atiming advance (TA) are used as an indicator, it is desirable to use theshorter of the two timer lengths obtained separately for the twoindicators, but the longer one may be used as necessary.

Next, the operation of a base station (Node B) according to thisexemplary embodiment will be described.

FIGS. 15 to 17 are flow charts showing the operation of the base stationaccording to the first exemplary embodiment of the present invention.FIG. 15 shows the operation in the case of a deemed out-of-sync state.FIG. 16 shows the operation in the case of a deemed in-sync state. FIG.17 shows the operation to determine and update a timer length.

Referring to FIG. 15, which relates to the case of a deemed out-of-syncstate, the base station (Node B) 102 initializes the first timer(T_SYNC=T) (step S101) and determines whether or not the basic signal(random access signal) has been received (step S102).

The following assumptions are used here.

Firstly, the base station (Node B) 102 assigns a radio resource fortransmission of an uplink signal such that an uplink signal (other thana random access signal) from the mobile station (UE #m) 101 is alwaysreceived before the timer times out. Therefore, a situation never occurswhere an uplink signal is received after a timeout of the timer.

Secondly, the length (set value) of the first timer held by the basestation (Node B) 102 is the same as the length of the second timer heldby the mobile station (UE #m) 101.

Thirdly, the calculation of a timing advance (TA) is performed atregular time intervals. It should be noted that calculation at regulartime intervals is employed by way of an example and that a timingadvance (TA) may be calculated every time an uplink signal is received.

Fourthly, a timing advance (TA) is transmitted to the mobile stationevery time it is calculated. Since a determination based on a thresholdis not necessary, it is guaranteed that the next timing advance (TA) iscalculated before a timeout. However, if the base station (Node B) 102has not received or transmitted any data for a certain fixed period andthus does not need to maintain synchronization any more, it returns theinformation concerning the mobile station to a deemed out-of-sync stateupon a timeout, without instructing the mobile station to transmit anuplink signal for calculation of a timing advance (TA).

Although the present invention also allows the determination and updateof a timer length to be performed at regular time intervals (or inresponse to a certain trigger event) (which similarly applies to theother exemplary embodiments described below), this exemplary embodimentis described only with respect to the selection part which selectsbetween whether or not a timer length will be determined.

If it determines that a basic signal (random access signal) has beenreceived, the base station (Node B) 102 calculates a timing advance (TA)(step S103) and stores the calculated timing advance (TA) (step S104);transmits the timing advance (TA) to the mobile station (UE #m) 101(step S105); and causes the first timer to start operating (step S106).On the other hand, if it determines that a basic signal (random accesssignal) has not been received, the base station (Node B) 102 does notperform the processes of steps S103 to S106.

As shown in FIG. 16, in the case of a deemed in-sync state, the basestation (Node B) 102 determines whether the value T_SYNC of the firsttimer is 0 or not (step S101). If the value is 0, the base station (NodeB) 102 ends the process. Otherwise, it determines whether or not anuplink signal has been received (step S202).

If it determines that an uplink signal has been received, base station(Node B) 102 determines whether or not to calculate a timing advance(TA) (step S203). Otherwise, it ends the process.

If it determines that a timing advance (TA) should be calculated, thebase station (Node B) 102 calculates a timing advance (TA) (step S204);stores the calculated timing advance (TA) in the TA storage part 1132(step S205); transmits the timing advance (TA) to the mobile station (UE#m) 101 (step S206); resets the first timer (step S207); and starts thefirst timer (step S208). Otherwise, the base station (Node B) 102 doesnot perform the processes of steps S204 to S208.

As shown in FIG. 17, the base station (Node B) 102 determines whether ornot to update the first timer (step S301). If it determines that thefirst timer does not have to be updated, it ends the process.

If it determines that the first timer should be updated, the basestation (Node B) 102 invokes the timing advance (TA) (step S302);calculates the rate of variation in the timing advance (TA) (step S303);determines the first timer length T′ after updating (step S304);transmits the updated value T′ for the first timer to the mobile station(UE #m) 101 (step S305); and updates the length of the first timer to T′(step S306).

Possible locations to insert the operation to determine and update atimer length shown in FIG. 17 include immediately after the conditionalbranch at step S202 performed in the case of a deemed in-sync state inFIG. 16 or before the timer reset process at step S207. However, theselocations are examples only and not limited to these.

It is also possible to change the intervals at which to update atransmit timing from the mobile station (UE #m), proportionally to thelength of the first and second timers determined for each mobile station(UE #m).

An example hardware structure for the mobile station (UE #m) 101 and thebase station (Node B) 102 will now be described.

FIG. 18 is a block diagram showing the hardware structure of the mobilestation 101 and the base station 102 according to this exemplaryembodiment of the present invention.

As shown in FIG. 18, the mobile station 101 and

the base station 102 according to the present invention may be realizedin any hardware structure similar to general computer devices, andmainly comprises a CPU (Central Processing Unit) 1001; a main storagepart 1002 which is a main memory, such as a RAM (Random Access Memory),used as data workspace and temporary save space for data; acommunication part 1003, which transmits and receives data via thenetwork 2000; a presentation part 1004, such as an LCD, printer andspeakers; an input part 1005, such as a keyboard and mouse; an interfacepart 1006, which is connected with peripherals to performtransmission/reception of data; an auxiliary storage part 1007, which isa hard disc devise consisting of a nonvolatile memory, such as a ROM(Read Only Memory), magnetic disc and semiconductor memory; and a systembus 1008, which connects between the above-mentioned components of thisinformation processing unit.

It goes without saying that the operations of the mobile station 101 andthe base station 102 according to the present invention can be realizedin hardware form by implementing within the mobile station 101 and thebase station 102 a circuit component which consists of an LSI (LargeScale Integration) or other hardware parts into which a program thatrealizes these functions is incorporated, but these operations can alsobe realized in software form by causing the CPU 1001 on the computerprocessing unit to execute a program which provides the functions ofthese components.

In other words, the CPU 1001 can realize the above-described functionsin a software-based manner by loading a program stored in the auxiliarystorage part 1007 into the main storage part 1002 and executing theprogram to control the operations of the mobile station 101 and the basestation 102.

The mobile station and the base station in the exemplary embodimentsdescribed below have a similar structure to the above, and the functionsdescribed above may be realized in a hardware- or software-based manner.

(Effects of the First Exemplary Embodiment)

As described above for the first exemplary embodiment, the presentinvention makes it possible to adaptively control a timer fordetermining for each mobile station (UE) whether it is in a deemedin-sync state or in a deemed out-of-sync state. By this, the probabilitycan be reduced that a mobile station actually in sync is judged to beout of sync. In the case of LTE, it is also possible to reduce theprobability that a latency before transmission of data caused by thenecessity for a mobile station (UE) actually in sync to transmit aNon-sync RACH before transmitting a Scheduling Request.

Second Exemplary Embodiment

FIG. 19 is a block diagram showing the system structure of a wirelesscommunication system according to a second exemplary embodiment of thepresent invention. In this exemplary embodiment, the calculation of anindicator value for determining the length of the first and secondtimers, as well as the determination of the length of the first timer,are performed by the base station, and the determination of the lengthof the second timer is performed by the mobile station.

With reference to FIG. 19, the mobile station (UE) 201 comprises adetermination part 103, a basic signal generation part 104, an uplinksignal generation part 105, a transmit information input part 106, asignal transmission part 107, a downlink signal demodulation part 203, atimer determination part 204 and a second timer 205.

At the mobile station (UE #m) 201, the downlink signal demodulation part203 receives from the base station (Node B) 202 a downlink receivesignal S_(DLTX), which contains a timing advance (TA) for a transmittiming, and outputs the reproduced timing advance (TA) S_(RTA), whichcorresponds to the received timing advance (TA); timer controlinformation S_(TCI), which notifies a reset of the second timer when atiming advance (TA) is notified from the base station (Node B); and areproduced indicator value S_(RID), which corresponds to the indicatorused for determination by the base station (Node B) of the length of thefirst timer #m if the first timer #m is updated at the base station(Node B).

The timer determination part 204 determines the length of the secondtimer using the reproduced indicator value S_(RID) as input, and outputsthe result as timer update information S_(TUIU).

The second timer 205 operates according to the timer control informationS_(TCI) and the timer update information S_(TUIU). When the timer updateinformation S_(TUIU) is inputted, the second timer 205 updates thelength of the second timer, and outputs as state information S_(SI) theinformation as to whether the mobile station (UE) #m is in a deemedin-sync state or in a deemed out-of-sync state.

When transmit information S_(INFO) to be transmitted to the base station(Node B) is inputted, the determination part 103 switches connectionaccording to the state information S_(SI). More specifically, itswitches connection to the uplink signal generation part 105 if theinformation indicates a deemed in-sync state or to the basic signalgeneration part 104 if the information indicates a deemed out-of-syncstate.

The random access signal generation part 104 generates and outputs arandom access signal S_(RS), which is necessary to receive from the basestation (Node B) a timing advance (TA) for synchronizing an uplinksignal.

The uplink signal generation part 105 adjusts the transmit timingaccording to the reproduced timing advance (TA) S_(RTA), and generatesand outputs an uplink signal S_(US) that contains the transmitinformation S_(INFO).

As an uplink transmit signal S_(ULTX), the signal transmission part 107transmits the uplink signal S_(US) if the mobile station is in a deemedin-sync state or the random access signal S_(RS) if the mobile stationis in a deemed out-of-sync state.

Referring to FIG. 19, the base station (Node B) 202 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 112, a timing calculation part 113, a timeradaptive control part 206, a synchronization timer 207 and a downlinktransmission part 208.

At the base station (Node B) 202, the determination part 110 switchesconnection according to the state information S_(SI), which indicatesthe state of the mobile station (UE) #m. More specifically, it switchesconnection to the uplink signal demodulation part 112 if the informationindicates a deemed in-sync state or to the basic signal demodulationpart 111 if the information indicates a deemed out-of-sync state.

The basic signal demodulation part 111 outputs as random accessdetection information S_(RDI) the information indicating a sequence thatexceeds the pre-defined detection threshold, by using as input theuplink received signal S_(ULTX) corresponding to the random accesssignal S_(RS).

The uplink signal demodulation part 112 demodulates an uplink receivedsignal S_(ULTX), which corresponds to an uplink signal S_(US), andoutputs reproduced transmit information S_(RINFO), which corresponds totransmit information S_(INFO).

The timing calculation part 113 detects the receive timing of an uplinkreceived signal S_(ULTX) and, based on the receive timing, calculatesand outputs the timing advance (TA) S_(TA) to be notified to the mobilestation (UE) #m.

The timer adaptive control part 206, using as input both or either of anuplink received signal S_(ULTX) and/or a timing advance (TA) S_(TA),calculates as indicator value information S_(ID) an indicator fordetermining the length of the first timer #m and the second timer of themobile station (UE) #m. Using the indicator value information S_(ID), itdetermines the length of the first timer #m as timer update informationS_(TUIN). The timer adaptive control part 206 then outputs the resultantindicator value information S_(ID), the resultant timer updateinformation S_(TUIN), as well as the information which notifies anupdate of the first timer #m by sending a timing advance (TA) to themobile station (UE) #m as timer control information S_(TCI). Theindicator value information S_(ID) indicates the traveling speed and thevariation in the transmit timing that have actually been used fordetermination of the timer length.

The synchronization timer 207, which has an M number of first timers,operates according to the timer update information S_(TUIN) and thetimer control information S_(TCI), and outputs as state informationS_(SI) the information as to whether the mobile station (UE) #m is in adeemed in-sync state or in a deemed out-of-sync state.

The downlink transmission part 208, according to the state informationS_(SI), generates and transmits a downlink transmit signal S_(DLTX). Thedownlink transmit signal S_(DLTX) contains a timing advance (TA) S_(TA)and indicator value information S_(TD) in the case of a deemed in-syncstate or contains a timing advance (TA) S_(TA), indicator valueinformation S_(ID) and random access detection information S_(RDI) inthe case of a deemed out-of-sync state.

When determining the length of the first timer #m, the timer adaptivecontrol part 206 uses as an indicator both or either of a travelingspeed S_(VI), which is the result obtained by estimating the travelingspeed of the mobile station (UE) #m, and/or transmit timing variationinformation S_(TADI), which is the result obtained by calculating a timevariation in the timing advance (TA) and outputs one or both of these,as applicable, as indicator value information S_(ID).

FIGS. 20 to 22 show the structure of the timer adaptive control partwhen using as an indicator a traveling speed and a time variation in atiming advance (TA); a traveling speed; or a time variation in a timingadvance (TA), respectively.

The timer adaptive control part 206 of FIG. 20 comprises a speedestimation part 209, which estimates the traveling speed S_(VI) of themobile station (UE) #m by using as input an uplink received signalS_(ULTX); a variation calculation part 210, which calculates and outputsthe time variation S_(TADI) in the timing advance (TA) by using as inputa timing advance (TA) S_(TA); and a timer determination part 211, whichdetermines the length of the first timer #m by using as input thetraveling speed S_(VI) and the time variation S_(TADI) in the timingadvance (TA). The timer adaptive control part 206 outputs the travelingspeed S_(VI) and the time variation S_(TADI) in the timing advance (TA)as indicator value information S_(ID).

The timer adaptive control part 206 of FIG. 21 comprises a speedestimation part 209, which estimates the traveling speed S_(VI) of themobile station (UE) #m by using as input an uplink received signalS_(ULTX), and a timer determination part 212, which determines by usingthe traveling speed S_(VI) as input the timer length for the first timer#m. The timer adaptive control part 206 outputs the traveling speedS_(VI) as indicator value information S_(ID).

The timer adaptive control part 206 of FIG. 22 comprises a variationcalculation part 210, which calculates and outputs the time variationS_(TADI) in the timing advance (TA) by using a timing advance (TA)S_(TA) as input, and a timer determination part 213, which determines byusing the time variation S_(TADI) in the timing advance (TA) as inputthe timer length for the first timer #m and outputs the time variationS_(TADI) of the timing advance (TA) as indicator value informationS_(ID).

FIG. 23 is a diagram for explaining the procedure to determine andupdate the length of the first and second timers according to the secondexemplary embodiment. The timer adaptive control part 206 is assumed tocomprise a speed estimation part 209 and a timer determination part 210(FIG. 21). The timer determination part 204, 212 determines the lengthof the first and second timers, based on the traveling speed S_(VI) andthe table which pre-defines correlations between traveling speed andtimer length.

The base station (Node B) performs the reception of an uplink signal 1from the mobile station (UE) #m, the calculation of a timing advance(TA) and the estimation of a traveling speed. The base station (Node B)causes the timer determination part 206 to determines the length offirst timer #m based on the traveling speed and the table, updates thelength of the first timer #m, and notifies the timing advance (TA) andthe traveling speed to the mobile station (UE) #m via a downlink signal1.

Immediately after transmitting the downlink signal 1 to the mobilestation (UE) #m, the base station (Node B) resets the first timer #m andcauses the first timer #m to start operating again.

The mobile station (UE) #m demodulates the downlink signal 1 toreproduce the timing advance (TA) and the traveling speed. The mobilestation (UE) #m determines the length of the second timer through thetimer determination part 204 based on the reproduced traveling speed andthe table, updates the length of the second timer and causes the secondtimer to start operating again. The mobile station (UE) #m then adjuststhe transmit timing according to the reproduced timing advance (TA) andtransmits an uplink signal 2.

If the same indicator is used as the first exemplary embodiment, theabove-described adaptive control process using the table is performedsimilarly to the first exemplary embodiment.

A possible signal that can be used by the speed estimation part of thebase station (Node B) for estimation of a traveling speed is a knownsignal (Reference Signal: RS) for demodulating the data from the mobilestation (UE) transmitted via the Uplink Shared Channel (UL-SCH) and theuplink signal including the control information, or an RS for CQImeasurement which is transmitted to allow the base station (Node B) tomeasure the quality of an uplink line (Channel Quality Indicator: CQI)transmitted via a UL-SCH. Also, a possible signal that can be used fornotifying a traveling speed is a signal for data transmission (PhysicalDownlink Shared Channel: PDSCH) transmitted via a Downlink SharedChannel (DL-SCH).

(Effects of the Second Exemplary Embodiment)

As described above for the second exemplary embodiment, the presentinvention makes it possible to adaptively control a timer fordetermining on a per-mobile-station (UE) basis whether it is in a deemedin-sync state or in a deemed out-of-sync state. By this, the probabilitycan be reduced that a mobile station actually in sync is judged to beout of sync. In the case of LTE, it is also possible to reduce theprobability that a latency before transmission of data caused by thenecessity for a mobile station (UE) actually in sync to transmit aNon-sync RACH before transmitting a Scheduling Request.

Third Exemplary Embodiment

FIG. 24 is a block diagram showing the system structure of a wirelesscommunication system according to a third exemplary embodiment of thepresent invention. In this exemplary embodiment, the calculation of anindicator value for determining the length of the first and secondtimers, as well as the determination of the length of the first andsecond timers, are performed by the mobile station.

With reference to FIG. 24, the mobile station (UE) 301 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 303, a timer adaptive control part 304, asecond timer 305, and an uplink signal generation part 306.

At the mobile station (UE #m) 301, the downlink signal demodulation part303 receives from the base station (Node B) 302 a downlink receivesignal S_(DLTX) which contains a timing advance (TA) for a transmittiming, and outputs the reproduced timing advance (TA) S_(RTA), whichcorresponds to the received timing advance (TA).

The timer adaptive control part 304, using as input both or either ofthe reproduced timing advance (TA) S_(RTA) and/or a downlink receivesignal S_(DLTX), determines the length of the first timer #m and thesecond timer as timer update information S_(TUI). It then outputs timercontrol information S_(TCI), which notifies a reset of the second timerwhen the reproduced timing advance (TA) is inputted or when the lengthof the second timer is updated.

The second timer 305 operates according to the timer control informationS_(TCI) and the timer update information S_(TUI), and outputs as stateinformation S_(SI) the information as to whether the mobile station (UE)#m is in a deemed in-sync state or in a deemed out-of-sync state.

When transmit information S_(INFO) to be transmitted to the base station(Node B) is inputted, the determination part 103 switches connectionaccording to the state information S_(SI). More specifically, itswitches connection to the uplink signal generation part 306 if theinformation indicates a deemed in-sync state or to the basic signalgeneration part 104 if the information indicates a deemed out-of-syncstate.

The basic signal generation part 104 generates and outputs a randomaccess signal S_(RS), which is necessary to receive from the basestation (Node B) a timing advance (TA) for synchronizing an uplinksignal.

The uplink signal generation part 306 adjusts the transmit timingaccording to the reproduced timing advance (TA) S_(RTA), and generatesand outputs an uplink signal S_(US) that contains the transmitinformation S_(INFO) and the timer update information S_(TUI).

As an uplink transmit signal S_(ULTX), the signal transmission part 107transmits the uplink signal S_(US) if the mobile station is in a deemedin-sync state or the random access signal S_(RS) if the mobile stationis in a deemed out-of-sync state.

Referring to FIG. 24, the base station (Node B) 302 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 307, a timing calculation part 308, asynchronization timer 309 and a downlink transmission part 310.

At the base station (Node B) 302, the determination part 110 switchesconnection according to the state information S_(SI), which indicatesthe state of the mobile station (UE) #m. More specifically, it switchesconnection to the uplink signal demodulation part 307 if the informationindicates a deemed in-sync state or to the basic signal demodulationpart 111 if the information indicates a deemed out-of-sync state.

The basic signal demodulation part 111 outputs as random accessdetection information S_(RDI) the information indicating a sequence thatexceeds the pre-defined detection threshold, by using as input theuplink received signal S_(ULTX) corresponding to the random accesssignal S_(RS).

The uplink signal demodulation part 307 demodulates an uplink receivedsignal S_(ULTX), which corresponds to an uplink signal S_(US), andoutputs reproduced transmit information S_(RINFO), which corresponds totransmit information S_(INFO) and the reproduced timer updateinformation S_(RTUI), which corresponds to the timer update informationS_(TUI).

The timing calculation part 308 has a TA calculation part 3081 and a TAstorage part 3082. The timing calculation part 308 uses the TAcalculation part 3081 to detect the receive timing (i.e., a deviation inthe receive timing) for an uplink received signal S_(ULTX). The timingcalculation part 308 calculates a timing advance (TA) S_(TA) to notifyto the mobile station (UE) #m based on the detected receive timing, andstores the resultant TA in the TA storage part 3082. It then outputs thetiming advance (TA), as well as the information which notifies an updateof the first timer #m by sending a timing advance (TA) to the mobilestation (UE) #m as timer control information S_(TCI).

The synchronization timer 309, which has an M number of first timers,operates according to the reproduced timer update information S_(RTUI)and the timer control information S_(TCI), and outputs as stateinformation S_(SI) the information as to whether the mobile station (UE)#m is in a deemed in-sync state or in a deemed out-of-sync state.

The downlink transmission part 310, according to the state informationS_(SI), generates and transmits a downlink transmit signal S_(DLTX). Thedownlink transmit signal S_(DLTX) contains a timing advance (TA) S_(TA)in the case of a deemed in-sync state or contains a timing advance (TA)S_(TA) and random access detection information S_(RDI) in the case of adeemed out-of-sync state.

When determining the length of the first timer #m and the second timerof the mobile station (UE) #m, the timer adaptive control part 304 usesas an indicator both or either of a traveling speed S_(VI), which is theresult obtained by estimating the traveling speed of the mobile station(UE) #m, and/or transmit timing variation information S_(TADI), which isthe result obtained by calculating a time variation for the reproducedtiming advance (TA) S_(RTA). FIG. 25 shows the structure of the timeradaptive control part 304 when using as indicators both a travelingspeed and a time variation in a reproduced timing advance (TA).

The timer adaptive control part 304 of FIG. 25 comprises a speedestimation part 311, which estimates the traveling speed S_(VI) of themobile station (UE) #m by using as input a downlink receive signalS_(DLTX); a variation calculation part 312, which calculates and outputsthe time variation S_(TADI) in the reproduced timing advance (TA) byusing as input the reproduced timing advance (TA) S_(RTA); and a timerdetermination part 313, which determines the length of the first timer#m and the second timer of the mobile station (UE) #m by using as inputthe traveling speed S_(VI) and the time variation S_(TADI) in thereproduced timing advance (TA). The timer adaptive control part whichcomprises either of a speed estimation part 311 or a variationcalculation part 312, as well as a timer determination part 313, will beomitted from the description because it is the same as the firstexemplary embodiment described above (see FIGS. 3 and 10).

FIG. 26 is a diagram for explaining the procedure to determine andupdate a timer length according to the third exemplary embodiment. Thetimer adaptive control part 304 is assumed to comprise a speedestimation part and a timer determination part. The timer determinationpart determines the length of the timers, based on the traveling speedS_(VI) and the table which pre-defines correlations between travelingspeed and timer length.

The base station (Node B) receives an uplink signal 1 from the mobilestation (UE) #m and calculates a timing advance (TA). Immediately afternotifying the timing advance (TA) to the mobile station (UE) #m, thebase station (Node B) resets the first timer #m and causes the firsttimer #m to start operating again.

The mobile station (UE) #m receives a downlink signal 1 and performs thereproduction of a timing advance (TA) and the estimation of a travelingspeed. The mobile station (UE) #m determines the length of the firsttimer #m and the second timer, based on the estimated traveling speedand the table. The mobile station (UE) #m then updates and resets thesecond timer and causes the second timer to start operating again. Themobile station (UE) #m adjusts the transmit timing according to thereproduced timing advance (TA) and notifies the length of the firsttimer #m via an uplink signal to the base station.

The base station (Node B) receives the uplink signal 2 and reproducesthe length of the first timer #m determined by the mobile station (UE)#m. The base station (Node B) then updates the length of the first timer#m according to the reproduced value and causes the first timer #m tostart operating again.

A possible signal that can be used by the speed estimation part of themobile station (UE) for estimation of a traveling speed is a knownsignal (Reference Signal: RS, which is also called “Common PilotChannel: CPICH”), which is transmitted via a Downlink Shared Channel(DL-SCH). Also, a possible uplink signal that can be used for notifyingthe length of the timer is a signal for data transmission (PhysicalUplink Shared Channel: PUSCH) transmitted via an Uplink Shared Channel(UL-SCH).

(Effects of the Third Exemplary Embodiment)

As described above for the third exemplary embodiment, the presentinvention makes it possible to adaptively control a timer fordetermining on a per-mobile-station (UE) basis whether it is in a deemedin-sync state or in a deemed out-of-sync state. By this, the probabilitycan be reduced that a mobile station (UE) actually in sync is judged tobe out of sync. In the case of LTE, it is also possible to reduce theprobability that a latency before transmission of data caused by thenecessity for a mobile station (UE) actually in sync to transmit aNon-sync RACH before transmitting a Scheduling Request. In the casewhere the mobile station (UE) determines the length of the first timerheld by the base station (Node B), as is the case with this exemplaryembodiment, a downlink signal from the base station (Node B) may becomenecessary to indicate a permission of updating the length of the firsttimer.

Fourth Exemplary Embodiment

FIG. 27 is a block diagram showing the system structure of a wirelesscommunication system according to a fourth embodiment of the invention.In this exemplary embodiment, the calculation of an indicator value fordetermining the length of the first timer, as well as the determinationof the length of the first timer, are performed by the base station, andthe calculation of an indicator value for determining the length of thesecond timer, as well as the determination of the length of the secondtimer, are performed by the mobile station. It should be noted that theinformation used for calculation of an indicator value must be the samebetween the base station and the mobile station, so that the indicatorvalue calculated by the base station and the indicator value calculatedby the mobile station will become identical. In addition, controlinformation S_(CI) and reproduced control information S_(RCI) describedlater are conditional information necessary for measurement, rather thanindicator values. For example, the information would be a Dopplerfrequency if a traveling speed is used as an indicator.

Referring to FIG. 27, the mobile station (UE) 401 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 403, a timer adaptive control part 404, asecond timer 405, and an uplink signal generation part 406.

At the mobile station (UE #m) 401, the downlink signal demodulation part403 receives from the base station (Node B) 402 a downlink receivesignal S_(DLTX), which contains a timing advance (TA) for a transmittiming, and outputs the reproduced timing advance (TA) S_(RTA), whichcorresponds to the received timing advance (TA).

The timer adaptive control part 404, using as input both or either ofthe reproduced timing advance (TA) S_(RTA) and/or a downlink receivesignal S_(DLTX), determines the length of the second timer. It thenoutputs the resultant timer length as timer update information S_(TUIU),as well as the information which notifies a reset of the second timerwhen the reproduced timing advance (TA) is inputted or when the lengthof the second timer is updated as timer control information S_(TCI). Inaddition, the timer adaptive control part 404 also outputs as controlinformation S_(CI) the information used in the calculation of anindicator value for determining the length of the timer.

The second timer 405 operates according to the timer control informationS_(TCI) and the timer update information S_(TUIU), and outputs as stateinformation S_(SI) the information as to whether the mobile station (UE)#m is in a deemed in-sync state or in a deemed out-of-sync state.

When transmit information S_(INFO) to be transmitted to the base station(Node B) is inputted, the determination part 103 switches connectionaccording to the state information S_(SI). More specifically, itswitches connection to the uplink signal generation part 406 if theinformation indicates a deemed in-sync state or to the basic signalgeneration part 104 if the information indicates a deemed out-of-syncstate.

The basic signal generation part 104 generates and outputs a randomaccess signal S_(RS), which is necessary to receive from the basestation (Node B) a timing advance (TA) for synchronizing an uplinksignal.

The uplink signal generation part 406 adjusts the transmit timingaccording to the reproduced timing advance (TA) S_(RTA), and generatesand outputs an uplink signal S_(US) that contains the transmitinformation S_(INFO) and the control information S_(CI).

As an uplink transmit signal S_(ULTX), the signal transmission part 107transmits the uplink signal S_(US) if the mobile station is in a deemedin-sync state or the random access signal S_(RS) if the mobile stationis in a deemed out-of-sync state.

Referring to FIG. 27, the base station (Node B) 402 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 407, a timing calculation part 113, a timeradaptive control part 408, a synchronization timer 409 and a downlinktransmission part 410.

At the base station (Node B) 402, the determination part 110 switchesconnection according to the state information S_(SI), which indicatesthe state of the mobile station (UE) #m. More specifically, it switchesconnection to the uplink signal demodulation part 407 if the informationindicates a deemed in-sync state or to the basic signal demodulationpart 111 if the information indicates a deemed out-of-sync state.

The basic signal demodulation part 111 outputs as random accessdetection information S_(RDI) the information indicating a sequence thatexceeds the pre-defined detection threshold, by using as input theuplink received signal S_(ULTX) corresponding to the random accesssignal S_(RS).

The uplink signal demodulation part 407 demodulates an uplink receivedsignal S_(ULTX), which corresponds to an uplink signal S_(US), andoutputs the reproduced transmit information S_(RINFO), which correspondsto transmit information S_(INFO), as well as reproduced controlinformation S_(RCI), which corresponds to control information S_(CI).

The timing calculation part 113 detects the receive timing of an uplinkreceived signal S_(ULTX) and, based on the receive timing, calculatesand outputs the timing advance (TA) S_(TA) to be notified to the mobilestation (UE) #m.

The timer adaptive control part 408, using as input both or either of anuplink received signal S_(ULTX) and/or a timing advance (TA) S_(TA),determines the length of the first timer #m. It then outputs theresultant timer length as timer update information S_(TUIN), as well asthe information which notifies an update of the second timer by sendinga timing advance (TA) to the mobile station (UE) #m as timer controlinformation S_(TCI).

The synchronization timer 409, which has an M number of first timers,operates according to the timer update information S_(TUIN) and thetimer control information S_(TCI), and outputs as state informationS_(SI) the information as to whether the mobile station (UE) #m is in adeemed in-sync state or in a deemed out-of-sync state.

The downlink transmission part 410, according to the state informationS_(SI), generates and transmits a downlink transmit signal S_(DLTX). Thedownlink transmit signal S_(DLTX) contains a timing advance (TA) S_(TA)in the case of a deemed in-sync state or contains a timing advance (TA)S_(TA) and random access detection information S_(RDI) in the case of adeemed out-of-sync state.

When determining a timer length, the timer adaptive control part 404(408) uses as an indicator both or either of a traveling speed S_(VI),which is the result obtained by estimating the traveling speed of themobile station (UE) #m, and/or transmit timing variation informationS_(TADI), which is the result obtained by calculating a time variationin the reproduced timing advance (TA) S_(RTA) (timing advance (TA)S_(RTA)).

FIG. 28 shows the structure of the timer adaptive control part 404 (408)when using as indicators both a traveling speed and a time variation ina reproduced timing advance (TA).

The timer adaptive control part 404 (408) of FIG. 28 comprises a speedestimation part 411 (414), which estimates the traveling speed S_(VI) ofthe mobile station (UE) by using as input a downlink receive signalS_(DLTX) (uplink received signal S_(ULTX)); a variation calculation part412 (415), which calculates and outputs a time variation S_(TADI) in thereproduced timing advance (TA) by using as input the reproduced timingadvance (TA) S_(RTA) (timing advance (TA) S_(RTA)); and a timerdetermination part 413 (416), which determines the length of the secondtimer of the mobile station (UE) #m (first timer #m) by using as inputthe traveling speed S_(VI) and the time variation S_(TADI) in thereproduced timing advance (TA).

The method to determine and update the length of the first and secondtimers according to the fourth exemplary embodiment can be explained byuse of FIGS. 11 to 13 above.

The timer adaptive control part 404 (408) is assumed to comprise avariation calculation part 412 (415) and a timer determination part 413(416) (FIG. 28). The timer determination part determines the length ofthe first (second) timer, based on the time variation in the reproducedtiming advance (TA) and the table shown in FIG. 11 which pre-definescorrelations between time variation in timing advance (TA) and timerlength. In the description of this exemplary embodiment, the method tonotify the amount of deviation in a transmit timing as an absolute valuewill be considered as a method to notify the timing advance.

As explained above, each of the timer lengths in the table of FIG. 11has been calculated using the expressions (2) to (4) above, based ondifferent correlations between an amount of deviation in transmit timingduring an observation interval and a traveling speed at which suchamount of deviation is expected to occur.

In the expression (2), D_(TA) [usec] is the value of deviation in thetransmit timing; v [km/h] is the traveling speed of the mobile station(UE); t [sec] is the time which causes a deviation of D_(TA); and 6.7[usec/km] is a Round Trip Delay (RTD), which is a propagation delaycaused between the base station (Node B) and the mobile station (UE). Inthe expression (3), Δ d [usec] is the amount of deviation in thetransmit timing caused over a period of Δt [sec].

In this exemplary embodiment, a case will be considered where the mobilestation (UE) has succeeded in demodulating a downlink receive signal andwhere the value of the reproduced timing advance (TA) matches the valueof the timing advance (TA) calculated by the base station (Node B).

Suppose that the variation calculation part of the base station (Node B)calculates a time variation in a timing advance (TA) at regular timeintervals, i.e., per 10 [sec], for a mobile station (UE) #1 and that theresults are as shown in FIG. 12. At each of the times (t₀, t₁, t₂, t₃),the timer determination part determines the length of the first andsecond timers and controls these timers adaptively. It is assumed herethat the initial value T_(TM0) for the first and second timers is 1.5[sec] as described before, which is the length of time determined todeal with a traveling speed of 350 [km/h].

The time variation in the timing advance (TA) of a mobile station (UE)#1 at t₀ calculated by the variation calculation part of the basestation (Node B) is 2.18 [usec/10 sec]. Referring to the table of FIG.11, the variation is between 0.56 [usec/10 sec] to 2.23 [usec/10 sec],so the timer length can be made longer than the initial value 1.5 [sec].Based on the table, the length of the first timer #1 is determined to be4.5 [sec] and the length of the first timer #1 is updated.

Immediately after notifying the timing advance (TA) to the mobilestation (UE) #1, the base station (Node B) resets the first timer #1 andcauses the first timer #1 to start operating again.

On the other hand, at time t₀+τ (where τ is a processing latency fromwhen the base station (Node B) calculates a time variation in a timingadvance (TA) until when the mobile station (UE) #1 calculates a timevariation in the reproduced timing advance (TA)), the value of the timevariation in the reproduced timing advance (TA) resulting from thecalculation by the mobile station (UE) #1 is also 2.18 [usec/10 sec].Therefore, the length of the second timer is determined to be 4.5 [sec],based on the table of FIG. 11. The mobile station (UE) #1 then updatesand resets the second timer and causes the second timer to startoperating again.

Similarly, the time variations in the timing advance (TA) at t=t₁, t₂,t₃ calculated by the base station (Node B) and the time variations inthe reproduced timing advance (TA) at t=t₁+τ, t₂+τ, t₃+τ calculated bythe mobile station (UE) #m are 1.45 [usec/10 sec], 1.92 [usec/10 sec]and 3.28 [usec/10 sec]. Referring to the table of FIG. 11, it can bedetermined that the lengths of the first timer #1 and second timer ofthe mobile station (UE) #1 are 4.5 [sec], 4.5 [sec] and 1.5 [sec],respectively.

FIG. 13 shows the results of determining the first and second timers asdescribed above.

FIG. 29 is a diagram for explaining the procedure to determine andupdate a timer length according to the fourth exemplary embodiment.

The base station (Node B) receives an uplink signal 1 from the mobilestation (UE) #m, calculates a timing advance (TA) and then calculates atime variation in the timing advance (TA). The base station (Node B)determines and updates the length of the first timer #m, based on thecalculated time variation in the timing advance (TA) and the pre-definedtable. Immediately after notifying the timing advance (TA) to the mobilestation (UE) #m in a downlink signal 1, the base station (Node B) resetsthe first timer #m and causes the first timer #m to start operatingagain.

The mobile station (UE) #m receives and demodulates the downlink signal1 to reproduce the timing advance (TA). The mobile station (UE) #m thencalculates a time variation in the reproduced timing advance (TA), anddetermines the length of the second timer, based on the same pre-definedtable as the one used by the base station (Node B). Immediately afterupdating the length of the second timer, the mobile station (UE) #mresets the second timer and causes the second timer to start operatingagain. If the mobile station (UE) #m is rotating around the base station(Node B) while traveling, it is desirable to determine a timer lengthusing only a variation (time variation) as an indicator.

On the other hand, if a traveling speed is used as an indicator fordetermining a timer length in this exemplary embodiment, a possiblemethod that can be used is to either of the base station (Node B) or themobile station (UE) estimates a Doppler frequency from a known signaland notify the result of estimation to the other party.

As described above for the fourth exemplary embodiment, the presentinvention makes it possible to adaptively control a timer fordetermining on a per-mobile-station (UE) basis whether it is in a deemedin-sync state or in a deemed out-of-sync state.

(Effects of the Fourth Exemplary Embodiment)

According to this exemplary embodiment, by using the method describedabove, it becomes possible to reduce the probability that a mobilestation actually in sync is judged to be out of sync, because the timerlength can be controlled adaptively on a per-mobile-station basis. Inthe case of LTE, it is also possible to reduce the probability that alatency before transmission of data caused by the necessity for a mobilestation (UE) actually in sync to transmit a Non-sync RACH beforetransmitting a Scheduling Request.

Although, in the exemplary embodiments of the present inventiondescribed above, the length of the timer used for determining whetherthe mobile station (UE) is in a deemed in-sync state or in a deemedout-of-sync state based on its traveling speed or a time variation in atiming advance (TA) for a transmit timing, it is also possible todetermine the timer length by taking into account the services performedby each mobile station (UE). This is because the reading time variesdepending on which service is being performed. In this case, a longertimer length can be set for a longer reading time. It should be noted,however, that a longer timer length leads a greater possibility that amobile station goes out of sync before a timeout. To prevent thisproblem from occurring, it is necessary to establish and set anappropriate timer length that is deemed within an acceptable tolerance.

In addition, position information from GPS or other similar sources mayalso be used as a means to estimate a traveling speed.

Fifth Exemplary Embodiment

FIG. 30 is a block diagram showing the system structure of a wirelesscommunication system according to a fifth embodiment of the presentinvention.

Referring to FIG. 30, the mobile station (UE) 501 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 503, a timer adaptive control part 504, asecond timer 505, and an uplink signal generation part 506.

Also referring to FIG. 30, the base station (Node B) 502 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 507, a timing calculation part 508, a timerdetermination part 509, a synchronization timer 510 and a downlinktransmission part 511.

In this exemplary embodiment, the mobile station (UE) #m calculates thevalue of an indicator based on which to estimate an in-sync period,determines the length of the second timer so that it will be inverselyproportional to the indicator value, updates to the timer length thusdetermined and notifies the indicator value to the base station (NodeB). The base station (Node B), on the other hand, determines the lengthof the first timer #m so that it will be inversely proportional to thereproduced indicator value and updates to the timer length thusdetermined.

Sixth Exemplary Embodiment

FIG. 31 is a block diagram showing the system structure of a wirelesscommunication system according to a sixth embodiment of the presentinvention.

Referring to FIG. 31, the mobile station (UE) 601 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 603, an indicator value calculation part 604, asecond timer 605, and an uplink signal generation part 606. Theindicator value calculation part 604 comprises at least either of thespeed estimation part 344 and the variation calculation part 312 shownin FIG. 25.

Also referring to FIG. 31, the base station (Node B) 602 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 607, a timing calculation part 608, a timerdetermination part 609, a synchronization timer 610 and a downlinktransmission part 611.

In this exemplary embodiment, the mobile station (UE) #m calculates thevalue of an indicator based on which to estimate an in-sync period, andnotifies the indicator value thus calculated to the base station (NodeB). In turn, the base station (Node B) determines the length of both thefirst timer #m and the second timer of the mobile station (UE) #m sothat it will be inversely proportional to the reproduced indicatorvalue, updates the length of the first timer #1 and notifies the lengthof the second timer to the mobile station (UE) #m. The mobile station(UE) #m then reproduces the length of the second timer determined by thebase station (Node B) and updates the length of the second timeraccordingly.

Seventh Exemplary Embodiment

FIG. 32 is a block diagram showing the system structure of a wirelesscommunication system according to a seventh exemplary embodiment of thepresent invention.

Referring to FIG. 32, the mobile station (UE) 701 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 703, a timer determination part 704, a secondtimer 705, and an uplink signal generation part 706.

Also referring to FIG. 32, the base station (Node B) 702 comprises adetermination part 110, a basic signal demodulation part 111, an uplinksignal demodulation part 707, a timing calculation part 708, anindicator value calculation part 709, a synchronization timer 710 and adownlink transmission part 711. The indicator value calculation part 704comprises at least either of the speed estimation part 118 and thevariation calculation part 119 shown in FIGS. 3, 10 and 14.

In this exemplary embodiment, the base station (Node B) calculates thevalue of an indicator based on which to estimate an in-sync period, andnotifies the indicator value thus calculated to the mobile station (UE)#m. In turn, the mobile station (UE) #m determines the length of boththe first timer #m and the second timer so that it will be inverselyproportional to the reproduced indicator value, updates the length ofthe second timer and notifies the length of the first timer #m to thebase station (Node B). The base station (Node B) then reproduces thelength of the first timer #m determined by the mobile station (UE) #mand updates the length of the first timer #m accordingly.

Referring to FIG. 32, the mobile station (UE) 701 comprises adetermination part 103, a basic signal generation part 104, a transmitinformation input part 106, a signal transmission part 107, a downlinksignal demodulation part 703, a timer adaptive control part 704, asecond timer 705, and an uplink signal generation part 706.

Eighth Exemplary Embodiment

FIG. 33 is a block diagram illustrating a schematic concept of awireless communication system according to an eighth exemplaryembodiment of the present invention. The mobile station (UE) 801 and thebase station (Node B) of the present invention have one of thestructures of the exemplary embodiments described above. The presentinvention is applied in such a manner that, when the mobile station (UE)801 moves from within the communication coverage 8021 a of the basestation (Node B) 802 a to the communication coverage 8021 b of the basestation (Node B) 802 b, (1) the mobile station (UE) 801 receives anotification from the base station (Node B) 802 b; (2) in response tosuch notification, the mobile station (UE) 801 notifies the latest timerlength determined within the communication coverage 8021 a, based on oneof the structures of the above-described exemplary embodiments; and (3)the base station 802 b in turn notifies the timer length setting valueto the mobile station 801, using one of the methods described withrespect to the above-described exemplary embodiments.

According to this exemplary embodiment, even when a mobile station (UE)leaves the communication coverage of a base station (Node B) to another,it becomes possible to perform control of a timer which isper-mobile-station (UE) basis adaptively for determining whether themobile station is in a deemed in-sync state or in a deemed out-of-syncstate between the mobile station (UE) and such another base station(Node B).

Ninth Exemplary Embodiment

FIG. 34 is a block diagram illustrating a schematic concept of awireless communication system according to a ninth exemplary embodimentof the present invention. The mobile station (UE) and the base station(Node B) of this exemplary embodiment have one of the structures of theexemplary embodiments described above. The present invention is appliedin such a manner that, when the mobile station (UE) 801 moves fromwithin the communication coverage 8021 a of the base station (Node B)802 a to the communication coverage 8021 b of the base station (Node B)802 b, (1) the mobile station (UE) 801 responds in the manner describedwith respect to the above-described exemplary embodiments; (2) the basestation (Node B) 802 b requests the base station (Node B) 802 a forinformation concerning the mobile station (UE) 801, using one of themethods described with respect to the above-described exemplaryembodiments; (3) in response to this request, the base station (Node B)802 a notifies the information concerning the mobile station (UE) 801 tothe base station (Node B) 802 b; and (4) based on the informationnotified from the base station (Node B) 802 a, the base station 802 bnotifies the timer length setting value to the mobile station 801. Morespecifically, if a handover of a mobile station to another base stationoccurs, the latest timer length being used by the original base stationis transferred from the original base station to such another basestation to which the mobile station is handed over.

According to this exemplary embodiment, even when a mobile station (UE)leaves the communication coverage of a base station (Node B) to another,it becomes possible between different base stations (Node B) to reducesignalling and to perform control of a timer which is per-mobile-station(UE) basis adaptively for determining whether the mobile station is in adeemed in-sync state or in a deemed out-of-sync state, becauseinformation concerning the mobile station (UE) is passed between theoriginal and current (new) base stations (Node B).

Tenth Exemplary Embodiment

FIG. 35 is a diagram illustrating a schematic concept of a wirelesscommunication system according to a tenth exemplary embodiment of thepresent invention. The mobile station (UE) and the base station (Node B)of this exemplary embodiment have one of the structures of the exemplaryembodiments described above. The present invention is applied in such amanner that, when the mobile station (UE) 801 moves from within thecommunication coverage 8021 a of the base station (Node B) 802 a to thecommunication coverage 8021 b of the base station (Node B) 802 b, (1)the base station 802 a notifies to the base station 802 b the latestlength of the timer of the mobile station 801, in addition to theinformation necessary for a handover; (2) the mobile station 801notifies to the base station 802 b that it has been handed over from thebase station 802 a; and (3) the base station 802 a notifies to themobile station 801 the latest timer length setting value notified fromthe base station 802 a. More specifically, if a handover of a mobilestation to another base station occurs, the latest timer length beingused by the original base station is transferred from the original basestation to such another base station to which the mobile station ishanded over.

According to this exemplary embodiment, even when a mobile station (UE)leaves the communication coverage of a base station (Node B) to another,it becomes possible between different base stations (Node B) to reducesignalling and to perform control of a timer which is per-mobile-station(UE) basis adaptively for determining whether the mobile station is in adeemed in-sync state or in a deemed out-of-sync state, becauseinformation concerning the mobile station (UE) is passed between theoriginal and current (new) base stations (Node B).

First Example

An example of the present invention will now be described.

A TA is a signal obtained by detection of time synchronization and issent from a base station to a mobile station. The mobile stationcorrects a propagation delay and adjusts a transmit timing by using theTA, so that a timing deviation from uplink signals sent from othermobile stations will fall within the receiver window. Time-divisionmultiplexing of an uplink using a TA is performed in order to preventoverlapping of transmissions via uplinks from a plurality of mobilestations.

Timing control becomes necessary when:

(1) a mobile station accesses a cell for the first time, which includesan initial access and a state transition from idle to active;

(2) a mobile station accesses a cell after a long-term DTX; or

(3) the base station judges that a TA must be transmitted, whichsituation may occur, for example, during data transmission.

If a cell (in particular, a cell with a small radius) in whichoverlapping of uplink signals is not expected to occur during themaximum propagation delay, timing control for uplinks may not berequired.

TA commands may have different control accuracy as described below:

(1) one-bit TA command, which has low reliability but is frequentlytransmitted; or

(2) multiple-bit TA command, which has high reliability but isinfrequently transmitted.

A mobile station is not aware of the actual synchronization timing at abase station. A base station, on the other hand, can recognize whetheror not a mobile station is actually in sync, from the reference signalof an uplink, data signal or the control signal.

A mobile station may be in either of the two states, which can be judgedby use of a TA (TA state):

(1) IN-SYNC state; or

(2) OUT-OF-SYNC state.

The mobile station determines its TA state according to the followingrules:

(1) A mobile station enters an IN-SYNC state when receiving a one- ormultiple-bit TA command, causing a timer called T_SYNC to startoperating; and

(2) A mobile station enters an OUT-OF-SYNC state when the timer T_SYNCtimes out.

The value of the timer T_SYNC is notified from a base station to amobile station upon establishment or re-establishment of an RRC.

T_SYNC is controlled on a per-mobile-station basis and is optimizedaccording to the channel status specific to each mobile station. Forexample, a base station can set a small value as the initial value ofT_SYNC and later change it to a larger value with respect to a mobilestation if the mobile station is taking much longer time than othersbefore entering an OUT-OF-SYNC state.

A control of T_SYNC can be maintained across a handover to another cell.When a handover occurs between different base stations, the same T_SYNCvalue can be set before and after the handover between these basestations, by using either of the following procedures: the mobilestation notifies the length of its timer to the target base station towhich the mobile station is handed over, or the source base stationtransfers the latest timer length being used within the source cell tothe target base station. When a mobile station moves from one cell toanother of the same base station, the base station can set the sameT_SYNC value before and after a handover.

The first to ninth exemplary embodiments can be applied to such controlof T_SYNC.

In order to solve the subjects described above, a wireless communicationsystem as described below is provided.

In a wireless communication system provided by the present invention,

a base station (Node B) holds a first timer for judging whether a mobilestation (UE) is in a deemed in-sync state or in a deemed out-of-syncstate, one for each of M mobile stations (UE) (where M is a naturalnumber), i.e., M first timers in total;

with respect to uplink signals of the mth (where m is an integer between1 and M) mobile station (UE) #m, the base station (Node B) calculates atiming advance (Timing Advance: TA) of a transmit timing, which isnecessary for uplink signals from M mobile stations (UE) to synchronizewith each other at the base station (Node B) and, immediately afternotifying the timing advance (TA) to the mobile station (UE) #m, causesthe first timer #m for judging whether the mobile station (UE) #m is ina deemed in-sync state or in a deemed out-of-sync state to operate;

immediately after being notified the timing advance (TA), the mobilestation (UE) #m causes the second timer used for judging its own stateto operate, adjusts a transmit timing according to the timing advance(TA), modifies the format of an uplink signal according to its ownstate, and transmits the resultant uplink signal; and

both or either of the base station (Node B) and/or the mobile station(UE) #m adaptively determine(s) and update(s) the length of both oreither of the first timer #m and/or the second timer according to thevalue of an indicator based on which to estimate an in-sync period inwhich the mobile station (UE) #m in a deemed in-sync state becomes in adeemed out-of-sync state.

The structure of the wireless communication system according to each ofthe exemplary embodiments will be summarized below.

The first wireless communication system has a structure wherein the basestation (Node B) calculates the value of an indicator based on which toestimate an in-sync period, determines the length of both the firsttimer #m and the second timer of the mobile station (UE) #m so that itwill be inversely proportional to the indicator value, updates thelength of the first timer #m, and notifies the length of the secondtimer thus determined to the mobile station (UE) #m; and the mobilestation (UE) #m reproduces the length of the second timer determined bythe base station (Node B), and updates the length of the second timeraccordingly.

The second wireless communication system has a structure wherein thebase station (Node B) calculates the value of an indicator based onwhich to estimate an in-sync period, determines the length of the firsttimer #m so that it will be inversely proportional to the indicatorvalue, updates the length of the first timer #m, and notifies theindicator value to the mobile station (UE) #m; and the mobile station(UE) #m determines the length of the second timer so that it will beinversely proportional to the reproduced indicator value, and updatesthe length of the second timer.

The third wireless communication system has a structure wherein themobile station (UE) #m calculates the value of an indicator based onwhich to estimate an in-sync period, determines the length of both thefirst timer #m and the second timer so that it will be inverselyproportional to the indicator value, updates the length of the secondtimer, and notifies the length of the first timer #m thus determined tothe base station (Node B); and the base station (Node B) reproduces thelength of the first timer #m determined by the mobile station (UE) #m,and updates the length of the first timer #m accordingly.

The fourth wireless communication system has a structure wherein themobile station (UE) #m calculates the value of an indicator based onwhich to estimate an in-sync period, determines and updates the lengthof the second timer so that it will be inversely proportional to theindicator value, and notifies the indicator value to the base station(Node B); and the base station (Node B) determines and updates thelength of the first timer #m so that it will be inversely proportionalto the reproduced indicator value.

The fifth wireless communication system has a structure wherein the basestation (Node B) and the mobile station (UE) #m individually calculatethe value of an indicator based on which to estimate an in-sync period,and individually determine and update the length of the first timer #mand the second timer so that they will be inversely proportional to theindicator value.

The sixth wireless communication system has a structure wherein themobile station (UE) #m calculates the value of an indicator based onwhich to estimate an in-sync period and notifies the value to the basestation (Node B); the base station (Node B) determines the length ofboth the first timer #m and the second timer of the mobile station (UE)#m so that it will be inversely proportional to the reproduced indicatorvalue, updates the length of the first timer #m, and notifies the lengthof the second timer to the mobile station (UE) #m; and the mobilestation (UE) #m reproduces the length of the second timer determined bythe base station (Node B), and updates the length of the second timeraccordingly.

The seventh wireless communication system has a structure wherein thebase station (Node B) calculates the value of an indicator based onwhich to estimate an in-sync period, and notifies the indicator value tothe mobile station (UE) #m; the mobile station (UE) #m determines thelength of both the first timer #m and the second timer so that it willbe inversely proportional to the reproduced indicator value, updates thelength of the second timer, and notifies the length of the first timer#m to the mobile station (UE) #m; and the base station (Node B)reproduces the length of the first timer #m determined by the mobilestation (UE) #m. and updates the length of the first timer #maccordingly.

As an indicator based on which to estimate an in-sync period, for use ineach wireless communication system provided by the present invention,both or either of the traveling speed of a mobile station (UE) and/or atime variation in a timing advance (TA), for example, can be used.

An example of method to determine the length of the first and secondtimers according to the value of an indicator is to first prepare atable which pre-defines correlations between indicator and timer lengthand then to determine the timer length based on the calculated indicatorvalue and the table.

As explained in the foregoing, by adaptively controlling the length of atimer used for judging whether a mobile station is in a deemed in-syncstate or in a deemed out-of-sync state on a per-mobile-station basisregarding the traveling speed, the probability can be reduced that alatency before data transmission increases when the mobile station thatis actually in sync is judged to be out of sync.

While the present invention has been described by taking severalpreferred exemplary embodiments as examples, it should be appreciatedthat the invention is not limited to these exemplary embodiments but canbe embodied with a variety of modifications without departing from thespirit and scope of its technical principle.

1. A mobile station which performs communication with a base station,the mobile station comprising: a timer to count a period to judgewhether an uplink signal to the base station is synchronized, whereinthe period is sent from the base station which is capable of setting theperiod specific to the mobile station, and wherein the mobile stationrestarts the timer in response to receiving a timing adjustment valuefrom the base station.
 2. A method of controlling a mobile station whichperforms communication with a base station, the method comprising:counting a period of a timer to judge whether an uplink signal to thebase station is synchronized; and restarting the timer in response toreceiving a timing adjustment value from the base station, wherein theperiod is sent from the base station which is capable of setting theperiod specific to the mobile station.
 3. A wireless communicationsystem which performs communication between a mobile station and a basestation, wherein the mobile station comprises: a timer to count a periodto judge whether an uplink signal to the base station is synchronized,wherein the period is sent from the base station which is capable ofsetting the period specific to the mobile station, and wherein themobile station restarts the timer in response to receiving a timingadjustment value from the base station.
 4. A base station which performscommunication with a mobile station, the base station comprising: asetting unit to set a period of a timer of the mobile station, whereinthe period is used for judging whether an uplink signal from the mobilestation is synchronized, wherein the setting unit is capable of settingthe period specific to the mobile station; and a notification unit tonotify a timing adjustment value of the mobile station so that themobile station restarts the timer in response to receiving the timingadjustment value.